Influenza remains a major epidemic disease worldwide despite intensive vaccination programs. Webster et al., Nature, 296, 115-121 (1982) and Palese et al., Science, 215, 1469-1474 (1982). To date, vaccines for these efforts have utilized whole virus as antigen to elicit antibody responses against the particular influenza strain in circulation. Tyrrel et al., Br. Med. Bull., 35, 77-83 (1979).
These conventional vaccines suffer from several standpoints including poor characterization and non-uniformity due to production of virus in embryonated eggs, and can cause serious adverse side reactions. Most importantly, they suffer from a lack of generality required to be effective against the broad spectrum of influenza strains which can arise by genetic recombination. A well-defined vaccine which eliminates these problems is needed.
More recent work by Muller et al., Proc. Natl. Acad. Sci. USA, 79, 569-573 (January 1982), utilizing peptides as immunogens has been reported. In that work, immunogens were prepared utilizing a synthetic peptide corresponding to positions 91-108 of the HA.sub.1 subunit (the amino-terminal subunit) of the hemagglutinin (HA) molecule of a type A (H3N2) influenza virus. Muller et al. were able to provide a low level of neutralizing activity with sera obtained by immunizing with their peptide. In addition, Jackson et al., Virology, 120, 273-276 (1982) used a synthetic peptide whose amino acid residue sequence corresponded to positions 123-151 of the HA.sub.1 of the X-31 (H3N2) strain to raise antibodies that recognized the immunogenic peptide, but did not appear to bind to the virus itself.
We here present neutralization and protection studies utilizing antisera prepared against synthetic peptides corresponding to a number of regions of the influenza hemagglutinin (HA) molecule and describe and claim peptides, antisera and methods which are more efficient and well-characterized alternatives to standard, whole virus influenza vaccines and immunochemical methods.
The primary target of the neutralizaing response of vaccination is the hemagglutinin molecule which is the major surface glycoprotein of the virus. Dowdle et al., J.Virol., 13, 269-275 (1974). This hemagglutinin is synthesized in vivo as a precursor molecule (HA), and is subsequently cleaved proteolytically to two subunits, HA.sub.1 and HA.sub.2. Cleavage is necessary for the virus to be infective. Klenk et al., J. Virol., 69, 426-439 (1975) and Lazarowitz etal., Virology, 68, 440-454 (1975).
The sequences of the HA genes of several epidemic strains of influenza have been described and indicate that there is rapid genetic variation occurring within these genes. Laver et al., Nature, 283, 454-457 (1980); Webster et al, Virology, 104, 139-148 (1980); Wiley et al., Nature, 289, 373-378 (1981); and Gething et al., Nature, 187, 373-378 (1981). These mutational changes are reflected as alterations of the antigenic structure of HA allowing escape of the virus from the protection of the previous immunization, and the subsequent rise of a new epidemic strain. Moreover, serologically distinct viruses from previous epidemics occasionally reenter the population, possibly from non-human hosts, where they may have undergone genetic recombination.
It has been previously demonstrated that synthetic peptides corresponding to virutally all regions of the X-47 influenza virus HA (H3N2) [Min-Jou, Cell, 19, 683-696 (1980)] are capable of eliciting an immune response in experimental animals. Green et al., Cell, 28, 477-487 (1982). The antisera react strongly with the respective peptides, and in most cases also react with the homologous purified hemagglutinin molecule and the intact virus. Green et al., Cell, 28, 477-487 (1982) and Muller et al., Proc.Natl. Acad.Sci. USA, 79, 569-573 (1982).
The present results indicate that some antisera to synthetic peptides representing both the HA.sub.1 and HA.sub.2 subunits are capable of neutralizing X-47 influenza virus replication, and more importantly, are capable of protecting animal hosts from the disease caused by that virus. Moreover, these results also demonstrate that some sera against the synthetic peptide analogs of the influenza virus HA are capable of neutralizaing virus infections of differing hemagglutinin subtype.